LKB - Bose-Einstein condensates

2D rubidium Bose gases

Current team :  Jérôme Beugnon, Patricia Castilho, Jean Dalibard, Edouard Le Cerf, Sylvain Nascimbène, Raphaël Saint-Jalm, Jean-Loup Ville

Contacts :
Jérôme Beugnon
Sylvain Nascimbene
Jean Dalibard

Collège de France. 11 Place Marcelin Berthelot. 75005 Paris

     In the rubidium team we explore the physics of two-dimensional Bose gases. Starting from a 3D Bose-Einstein condensate we load atoms in a light sheet that strongly confine the atoms along the vertical direction to reach the 2D regime. Using an additional in-plane harmonic confinement we measured the equation state of the Bose gas in this regime and observed the Berezinskii-Kosterlitz-Thouless (BKT) crossover when we vary the reduced chemical potential of the cloud. We also demonstrated the superfluid character of the BKT phase by moving without dissipation an obstacle in the cloud. Recently, we realized in-plane box potentials with custom shapes that allow, for instance, to study the physics of uniform systems. We observed the emergence of coherence in these uniform systems after a quench cooling step. We detected the formation of topological defects (vortices or superfluid current in a ring) as predicted within the framework of the Kibble-Zurek mechanism.